PROBLEM TO BE SOLVED: To obtain a product, fry or parent fish of a flatfish belonging to a kind of flatfishes having at least good disease resistance and/or high growth characterisics, to provide a method for culturing and increasing the flatfishes by the use of the fry, to provide a method for culturing and increasing the flatfishes, while preventing the spreading of genetic pollution in environments, and to provide a method for culturing and increasing the flatfishes, making it impossible to reproduce the fry by a buyer. SOLUTION: This method for breeding a flatfish comprises genetically fixing good disease resistance as a good character to the flatfish, by the selection of a full homogenate derived by a genetic operation, preferably by the selection of a flatfish having the good character, while using ordinary fishes as control fishes, and subsequently mating the genetically fixed flatfish with a full homogenate or an ordinary flatfish to create the flatfish having the good character. The good characters are at least the good disease resistance and high growth characteristics of the flatfishes. The objective good characters are certified by evaluating the characteristics of the progenies of a flatfish belonging to the kind of the flatfish having the good characters by experiments in a practically culturing and producing scale.
